[Django]-How is it possible to use 1000 Heroku Dyno hours in one month?

As per the Heroku website I will get free 1000 dyno hours but what are these hours, I mean maximum number of hours in a month is 744 so how does it work?

Apps on Heroku can use more than one dyno:

• Some sites might want more than one web dyno to handle lots of traffic
• Some might run scheduled jobs, which run on separate one-off dynos
• Some might have background workers

Those hours all add up.